Artifical auris interna

ABSTRACT

A fishbone sensor ( 21 ) has a plurality of resonators resonating with sounds having different frequencies from each other and converts the vibration of each resonator into a signal corresponding to each vibration level. An amplifying circuit ( 22 ) amplifies the signal converted by the fishbone sensor ( 21 ) by a predetermined gain and supplies it to an external switch circuit ( 23 ). The external switch circuit ( 23 ) switches signal supply paths and sequentially sends supplied signals via an external antenna ( 24 ). An internal switch circuit ( 32 ) switches signal supply paths and sequentially supplies the signals sent via an internal antenna ( 31 ) to a plurality of electrodes ( 4   a ), thereby stimulating the nerves in the cochlea.

TECHNICAL FIELD

The present invention relates to an artificial ear.

BACKGROUND ART

Man can recognize a sound when a nerve in the cochlea, a part of theinternal ear, is stimulated.

Conventional artificial ears for helping the sense of hearing of thehearing-impaired people have a plurality of electrodes which areconnected to the nerves in the cochlea, and directly stimulate nervescorresponding to the frequencies of sounds occurring in the surroundingswith electricity.

The sounds occurring in the surroundings are collected by a microphoneand divided into respective frequencies through signal processing by aDSP (Digital Signal Processor). Each sound having its own frequency issent in the form of an electric signal to an electrode connected to anerve corresponding to the frequency.

However, real-time sound processing by a DSP has a problem that itcannot achieve both a low level of power consumption and a highresolution simultaneously.

For example, in order to process a sound in real time at a low level ofpower consumption, it is necessary to reduce the number of frequenciesto be processed, i.e., the number of electrodes for stimulating thenerves. However, this makes it impossible to realize a high resolution,and the sound to be perceived is unclear.

In order to process a sound to be perceived clearly and in real time, itis necessary to increase the number of frequencies to be processed,i.e., the number of electrodes for stimulating the nerves. Thisenormously increases the processes of the DSP and a low level of powerconsumption cannot be achieved.

For the reasons described above, the number of electrodes remains around10 to 25 in the conventional artificial ears.

DISCLOSURE OF INVENTION

Accordingly, an object of the present invention is to provide anartificial ear that realizes both a low level of power consumption and ahigh resolution simultaneously.

To achieve the above object, an artificial ear according to the presentinvention comprises: a sending unit (2) configured to convert a soundhaving a predetermined frequency into an electric signal and send theelectric signal; and a reception unit (3) configured to receive the sentelectric signal and apply it to a predetermined nerve in a cochlea,wherein

the sending unit (2) includes:

-   -   a plurality of resonators (21 b) which have resonant frequencies        different from each other and vibrate with sounds having same        frequencies as the resonant frequencies;    -   a conversion section (21) configured to convert vibration of        each of the plurality of resonators (21 b) into a signal        corresponding to level of the vibration; and    -   a sending section (28) configured to send a predetermined signal        among signals converted by the conversion section (21) to the        reception unit (3), and the reception unit (3) includes:    -   a plurality of electrodes (4 a) which are connected to nerves        present in the cochlea and each corresponding to different        frequencies from each other; and    -   a supply section (34) configured to supply a signal supplied        from the sending section (28) to a predetermined electrode among        the plurality of electrodes (4 a) thereby stimulating a nerve        corresponding to a predetermined frequency.

In the above-described configuration, the sending unit (2) may furtherinclude an amplifying section (22) configured to amplify a signalconverted by the conversion section (21) by a gain which varies inaccordance with the respective resonant frequencies possessed by theplurality of resonators (21 b).

In the above-described configuration, the sending section (28) mayinclude a first selection section (23) configured to select a signal tobe sent to the reception unit (3) from signals amplified by theamplifying section (22).

In the above-described configuration, the supply section (34) mayinclude a second selection section (32) configured to select anelectrode (4 a) to which a signal from the sending section (28) is to besupplied.

In the above-described configuration, the sending section (28) may senda start signal representing a start of operation by the first selectionsection (23) and an end signal representing an end of operation by thefirst selection section (23) to the reception unit (3) in order tosynchronize selection operations of the first selection section (23) andsecond selection section (32) with each other, and

the second selection section (32) may start operating in response to thestart signal and finishes operating in response to the end signal.

In the above-described configuration, the sending unit (2) may furtherinclude a storage section (25) configured to store gains for therespective resonant frequencies possessed by the plurality of resonators(21 b).

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a block diagram of an artificial ear according to anembodiment of the present invention;

FIG. 2 is a block diagram of a fishbone sensor possessed by a soundprocessing unit that constitutes the artificial ear of FIG. 1;

FIG. 3 is a flowchart showing a signal sending process performed by anexternal switch circuit of the sound processing unit that constitutesthe artificial ear of FIG. 1;

FIG. 4 is a flowchart showing a signal reception process performed by aninternal switch circuit of a reception unit that constitutes theartificial ear of FIG. 1; and

FIG. 5 is another block diagram of the artificial ear according to theembodiment of the present invention.

BEST MODE FOR CARRYING OUT THE INVENTION

An artificial ear according to an embodiment of the present inventionwill be explained below with reference to the drawings.

The artificial ear according to the embodiment of the present inventioncomprises a power source unit 1, a sound processing unit 2, a receptionunit 3, and an electrode section 4, as shown in FIG. 1.

The power source unit 1 comprises at least one of a dry battery, anaccumulator battery, a solar battery, a fuel battery, and a thermalpower generator, etc. as shown in FIG. 1, and supplies power to thesound processing unit 2.

The sound processing unit 2 is set near the external ear by, forexample, being caught on the auricle or in the earhole like an earphone.The sound processing unit 2 works by the power supplied from the powersource unit 1, and converts a sound having a predetermined frequency,among sounds occurring in the surroundings, into an electric signal. Thesound processing unit 2 sends the converted electric signal to thereception unit 3 in the form of a radio wave. The specific configurationof the sound processing unit 2 will be described later.

The reception unit 3 is implanted, for example, under the scalp near theexternal ear, and receives a radio wave from the sound processing unit2. The reception unit 3 supplies the electric signal supplied in theform of a radio wave to the electrode section 4. The specificconfiguration of the reception unit 3 will be described later.

The electrode section 4 includes a plurality of electrodes 4 a which areconnected to the nerves in the cochlea, and stimulates the nerves in thecochlear by applying thereto the electric signal supplied from thereception unit 3. The plurality of electrodes 4 a are respectivelyconnected to nerves corresponding to the frequencies of sounds detectedby the sound processing unit 2.

Next, the specific configuration of the sound processing unit 2 will beexplained.

As shown in FIG. 1, the sound processing unit 2 comprises a fishbonesensor 21, an amplifying circuit 22, an external switch circuit 23, anexternal antenna 24, an EEPROM (Electrically Erasable Programmable ReadOnly Memory) 25, and an I/O (Input/Output) circuit 26.

As shown in FIG. 2, the fishbone sensor 21 has a support shaft 21 a anda plurality of cantilevers (resonators) 21 b. The plurality ofcantilevers 21 b are formed on both sides of the support shaft 21 a andhave their one end fixed on the support shaft 21 a.

The plurality of cantilevers 21 b have their own different resonantfrequencies. The material and shape of each cantilever 21 b are selectedsuch that these resonant frequencies can be uniformly distributed in theman's audio range. The cantilevers 21 b are formed in a numbercorresponding to a frequency at which a sound occurring in thesurroundings can be clearly perceived by man (for example, the numberbeing 254).

When a sound occurring in the surroundings propagates through thesupport shaft 21 a, the cantilever 21 b that corresponds to thefrequency contained in the propagating sound vibrates at a strengthcorresponding to the strength of the sound having the correspondingfrequency.

The fishbone sensor 21 further has a detection circuit (unillustrated)which converts the vibration of each cantilever 21 g into an electricsignal. The vibration of each cantilever 21 b is detected by thedetection circuit and converted into a signal having a levelcorresponding to the strength of the vibration.

The detection circuit is, for example, a capacitor having the cantilever21 b functioning as one electrode thereof, and can detect the vibrationof the cantilever 21 b as changes in the capacitance of the capacitor.

After a sound is collected by a microphone, an output therefrom may beconnected to a piezoelectric element provided in the fishbone sensor 21.In this case, the size of the unit to be set around the external ear canbe reduced.

The fishbone sensor 21 outputs a signal generated in the way describedabove and having a level corresponding to the vibration level of eachcantilever 21 b to the amplifying circuit 22.

The amplifying circuit 22 connects a signal supply path between itselfand the external switch circuit 23 in accordance with the control of theexternal switch circuit 23, amplifies a signal supplied from thefishbone sensor 21 by a predetermined gain, and outputs the amplifiedsignal to the external switch circuit 23.

The amplifying circuit 22 has a cache memory 22 a for accumulating gainsto be described later which are stored in the EEPROM 25, and amplifiesthe signal from the fishbone sensor 21 by the gain accumulated in thecache memory 22 a.

The amplifying circuit 22 further has a timer (unillustrated) forcounting the time in which a signal supply path is connected. The timerstart counting a preset connection time when a signal supply path isconnected between the amplifying circuit 22 and the external switchcircuit 23. When the predetermined connection time passes, theamplifying circuit 22 disconnects the signal supply path that leads tothe external switch circuit 23.

The external switch circuit 23 controls the amplifying circuit 22 tosequentially switch signal supply paths between itself and theamplifying circuit 22 at predetermined timings. In other words, theexternal switch circuit 23 sequentially selects signals to be sent, fromamong signals amplified by the amplifying circuit 22 at predeterminedtimings one signal by one, and sends the signal to the reception unit 3via the external antenna 24.

The EEPROM 25 stores the gain for each frequency, that is used by theamplifying circuit 22 for amplifying a signal. The strength of anelectric signal stimulating a nerve in the cochlea varies depending onindividual persons and frequencies. Hence, the gain used by theamplifying circuit 22 is set for each frequency suitably for the user ofthe artificial ear.

The I/O circuit 26 is used for rewriting the gains stored in the EEPROM25.

As described above, the external switch circuit 23, the external antenna24, the EEPROM 25, and the I/O circuit 26 constitute a sending section28 for sending a predetermined signal, among signals converted by aconversion section, to the reception unit 3.

Next, the specific configuration of the reception unit 3 will beexplained.

As shown in FIG. 1, the reception unit 3 comprises an internal antenna31 and an internal switch circuit 32.

The internal antenna 31 receives a signal sent in the form of a radiowave from the external antenna 24 via the scalp, and supplies it to theinternal switch circuit 32.

The internal switch circuit 32 works by electricity supplied in the formof an electromagnetic wave via the internal antenna 31, and sequentiallyswitches signal supply paths between the internal antenna 31 and theplurality of electrodes 4 a at predetermined timings. In other words,the internal switch circuit 32 sequentially selects electrodes 4 a towhich a signal is to be supplied at predetermined timings one electrodeby one, and distributes signals supplied from the internal antenna 31 tothe plurality of electrodes 4 a.

In this way, the internal antenna 31 and the internal switch circuit 32constitute a supply section 34 for supplying a signal supplied from thesending section 28 to a predetermined electrode among the plurality ofelectrodes, thereby stimulating a nerve corresponding to a predeterminedfrequency.

The external switch circuit 23 and the internal switch circuit 32 aredesigned in advance in a manner that the timings at which signal supplypaths are switched are synchronous between them. Further, the connectiontime counted by the timer of the amplifying circuit 22 is preset so asto correspond to the interval at which the external switch circuit 23and the internal switch circuit 32 switch signal supply paths.

Next, the operation of the artificial ear according to the embodiment ofthe present invention will be explained.

When the sound processing unit 2 is turned on, the external switchcircuit 23 starts a signal sending process shown in FIG. 3.

First, the external switch circuit 23 reads the gain for each frequencyfrom the EEPROM 25 and writes it in the cache memory 22 a possessed bythe amplifying circuit 22 (step S101). As a result, the amplifyingcircuit 22 becomes able to amplify signals corresponding to respectivefrequencies supplied from the fishbone sensor 21 by predetermined gains.

When a sound occurs in the surroundings, the occurring sound propagatesthrough the support shaft 21 a of the fishbone sensor 21. Due to this,the cantilever 21 b that corresponds to the frequency contained in thepropagating sound vibrates at a strength corresponding to the strengthof the sound having the corresponding frequency.

The vibration of each cantilever 21 b is converted by the unillustrateddetection circuit into a signal having a level corresponding to thestrength of the vibration, and supplied to the amplifying circuit 22 tobe amplified.

After writing the gain for each frequency in the cache memory 22 a, theexternal switch circuit 23 outputs a start signal representing the startof an operation for switching signal supply paths to the amplifyingcircuit 22, and also sends it to the reception unit 3 via the externalantenna 24 (step S102).

Because of the start signal, the timing at which the external switchcircuit 23 starts switching operation and the timing at which theinternal switch circuit 23 starts switching operation can securely besynchronized.

The amplifying circuit 22 resets the timer in response to the startsignal from the external switch circuit 23.

After outputting the start signal, the external switch circuit 23controls the amplifying circuit 22 and switches signal supply paths toconnect a signal supply path for the process target cantilever 21 b tothe externalantenna 24 (step S103).

Specifically, the external switch circuit 23 outputs a switching signalinstructing switching of signal supply paths to the amplifying circuit22. In response to the switching signal from the external switchingcircuit 23, the amplifying circuit 22 connects a signal supply path forthe process target cantilever 21 b to the external switch circuit 23. Asa result, the process target cantilever 21 b and the external antenna 24are connected to each other.

When the signal sending process is started, a cantilever 21 bcorresponding to a preset frequency (for example, the highest frequency)is selected as the process target cantilever 21 b.

The signal from the process target cantilever 21 b is amplified by theamplifying circuit 22 by the predetermined gain stored in the cachememory 22 a and supplied to the external switch circuit 23.

The external switch circuit 23 sends the signal from the process targetcantilever 21 b supplied from the amplifying circuit 22 to the receptionunit 3 via the external antenna 24 (step S104).

As described above, the timer possessed by the amplifying circuit 22starts counting the preset connection time in response to the connectionof a signal supply path. When the predetermined connection time passes,the amplifying circuit 22 automatically disconnects the signal supplypath between itself and the external switch circuit 23.

When the signal supply path is disconnected, the external switch circuit23 determines whether the above-described process has been performed forall the cantilevers 21 b (or for all the frequencies) (step S105).

In a case where determining that the process has not been performed forall the cantilevers 21 b (or for all the frequencies) (step S105; NO),the external switch circuit 23 returns to the above step S103 to performthe above-described process for the next cantilever 21 b (or frequency).

To the contrary, in a case where determining that the process has beenperformed for all the cantilevers 21 b (or for all the frequencies)(step S105; YES), the external switch circuit 23 outputs an end signalrepresenting the end of the operation for switching the signal supplypaths to the amplifying circuit 22 and also sends it to the receptionunit 3 via the external antenna 24 (step S106).

Because of the end signal, the timing at which the external switchcircuit 23 ends the switching operation and the timing at which theinternal switch circuit 32 ends the switching operation can securely besynchronized.

In the way described above, the process for a sound occurring at aninstant is finished. In the sound processing unit 2, the process fromthe above-described steps S102 through S106 is repeated while the poweris turned on, thereby sounds occurring one after another are processedand sent to the reception unit 3.

In the meantime, the internal switch circuit 32 in the reception unit 3starts operating in response to the start signal supplied from the soundprocessing unit 2 via the internal antenna 31, and starts a signalreception process shown in FIG. 4.

First, the internal switch circuit 32 switches signal supply paths inthe manner of time division so as to synchronize with the soundprocessing unit 2, and connects an electrode 4 a which is connected to anerve corresponding to the frequency of the process target cantilever 21b to the internal antenna 31 (step S201). By doing so, the internalswitch circuit 32 selects the electrode 4 a connected to the nervecorresponding to the frequency of the process target cantilever 21 b asthe signal supply target.

When the signal reception process is started, the internal switchcircuit 32 selects an electrode 4 a connected to a nerve correspondingto a preset frequency (for example, the highest frequency) as the signalsupply target.

The internal switch circuit 32 supplies the signal supplied via theinternal antenna 31 to the selected supply target electrode 4 a (stepS202).

The nerve to which the supply target electrode 4 a is connected isstimulated by the supplied signal. Due to this, the user of theartificial ear can perceive the sound having the frequency correspondingto the stimulated nerve.

After supplying the signal, the internal switch circuit 32 determineswhether or not an end signal has been supplied from the sound processingunit 2 (step S203).

In a case where determining that an end signal has not been supplied(step S203; NO), the internal switch circuit 32 returns to theabove-described step S201 and performs the above-described process forthe next electrode 4 a.

To the contrary, in a case where determining that an end signal has beensupplied (step S203; YES), the internal switch circuit 32 finishes thesignal sending process and stops operating.

In the way described above, a sound occurring at a given instant isprocessed and transmitted to the nerve of the user.

As described above, using the fishbone sensor 21 having the cantilevers21 b that resonate with a variety of frequencies eliminates the need ofperforming complicated signal processing performed by the conventionalDSPs. It is therefore possible to largely increase the number offrequencies to be processed as compared with those conventionallyprocessed, while at the same time suppressing increase in the powerconsumed. As a result, a clearer and finer sound than obtained in aconventional manner can be perceived at a low level of powerconsumption.

Further, as described above, the internal switch circuit 32 startsoperating in response to a start signal supplied from the soundprocessing unit 2 and stops operating in response to an end signal.Therefore, the supply path switching operations performed by theexternal switch circuit 23 and internal switch circuit 32 can be moresecurely synchronized.

The above-described artificial ear may be provided with a capacitor 5between the internal switch circuit 32 and the electrodes 4 a as shownin FIG. 5, in order to smooth pulse signals supplied to the electrodes 4a in the time division manner from the internal switch circuit 32 a.

To make conversational sounds much clearer, the density of cantilevers21 b for the human vocalization frequency band may be increased withrespect to the densities for other frequency bands.

The fishbone sensor 21, the amplifying circuit 22, the external switchcircuit 23, the EPROM 25, and the I/O circuit 26 may be formed on onechip by a micromachine technology, a semiconductor manufacturingtechnique, etc. This makes it possible to realize a compact soundprocessing unit 2.

Cantilevers 21 b which resonate with sounds having frequencies out ofthe man's audio range may be provided so that sounds other than those inthe audio range can be transmitted to the nerves in the cochlear in theform of electric signals. With this configuration, sounds varying in abroader range than that of ordinary people or dogs can be perceived,allowing application to special purposes such as military use, etc.

The present invention is based on Japanese Patent Application No.2002-243426 filed on Aug. 23, 2002 and including specification, claims,drawings and summary. The disclosure of the above Japanese PatentApplication is incorporated herein by reference in its entirety.

Industrial Applicability

The present invention is very useful in industries concerning supportsfor the reduced hearing ability of hearing-impaired people or elderlypeople.

1. An artificial ear comprising: a sending unit (2) configured toconvert a sound having a predetermined frequency into an electric signaland send the electric signal; and a reception unit (3) configured toreceive the sent electric signal and apply it to a predetermined nervein a cochlea, characterized in that said sending unit (2) includes: aplurality of resonators (21 b) which have resonant frequencies differentfrom each other and vibrate with sounds having same frequencies as theresonant frequencies; a conversion section (21) configured to convertvibration of each of said plurality of resonators (21 b) into a signalcorresponding to level of the vibration; and a sending section (28)configured to send a predetermined signal among signals converted bysaid conversion section (21) to said reception unit (3), and saidreception unit (3) includes: a plurality of electrodes (4 a) which areconnected to nerves present in the cochlea and each corresponding todifferent frequencies from each other; and a supply section (34)configured to supply a signal supplied from said sending section (28) toa predetermined electrode among said plurality of electrodes (4 a)thereby stimulating a nerve corresponding to a predetermined frequency,and said plurality of resonators (21 b) have their ends at one side heldindependent from each other.
 2. The artificial ear according to claim 1,characterized in that said sending unit (2) further includes anamplifying section (22) configured to amplify a signal converted by saidconversion section (21) by a gain which varies in accordance with therespective resonant frequencies possessed by said plurality ofresonators (21 b).
 3. The artificial ear according to claim 2,characterized in that said sending section (28) includes a firstselection section (23) configured to select a signal to be sent to saidreception unit (3) from signals amplified by said amplifying section(22).
 4. The artificial ear according to claim 3, characterized in thatsaid supply section (34) includes a second selection section (32)configured to select an electrode (4 a) to which a signal from saidsending section (28) is to be supplied.
 5. The artificial ear accordingto claim 4, characterized in that said sending section (28) sends astart signal representing a start of operation by said first selectionsection (23) and an end signal representing an end of operation by saidfirst selection section (23) to said reception unit (3) in order tosynchronize selection operations of said first selection section (23)and second selection section (32) with each other, and said secondselection section (32) starts operating in response to the start signaland finishes operating in response to the end signal.
 6. The artificialear according to claim 2, characterized in that said sending unit (2)further includes a storage section (25) configured to store gains forthe respective resonant frequencies possessed by said plurality ofresonators (21 b).
 7. The artificial ear according to claim 1,characterized in that said plurality of resonators (21 b) have theirends at the other side connected to a support shaft (21 a) and supportedby said support shaft (21 a).
 8. The artificial ear according to claim7, characterized in that said plurality of resonators (21 b) arearranged on both sides of said support shaft (21 a).
 9. The artificialear according to claim 8, characterized in that said plurality ofresonators (21 b) have different lengths from each other and arearranged on said support shaft (21 a) in an order of a larger length toa smaller length from one end toward the other end of said support shaft(21 a).